Hepatitis B antibody was previously positive now 8 as a decrease in Hepatitis B surface antibody titer. Hepatitis B antibody is positive, i.e. hepatitis B surface antibody is positive. Hepatitis B surface antibody is a protective antibody. Positivity indicates immunity to HBV (hepatitis B virus) and is seen during recovery from hepatitis B, previous infections and after hepatitis B vaccination. Its positivity can last for many years, but the titer decreases gradually. Hepatitis B vaccination is given at birth or as an adult, and the body thus develops antibodies to hepatitis B. However, hepatitis B antibody titers are not static. As time passes, most of the antibody titers will drop, and some even become negative. Therefore, it is necessary to periodically review the hepatitis B two-half-pair test, and according to the results of the review, decide whether it is necessary to make up for the hepatitis B vaccine.